The Easy Way To Tell If You Have Drain Flies In Your Sink (& How To Get Rid Of Them)

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If you've noticed small, pesky flies flying around your kitchen or bathroom sink, you may have a drain fly problem. It can be hard to notice the key differences between drain flies and fruit flies due to their similar small size, but drain flies are almost exclusively found near plumbing because they feed on the slime or muck that builds on the sides of drains. Adults flying around a drain is a fairly clear sign, but you could confirm whether you have drain flies by placing a trap over your sink and checking whether it catches any flies. Any insects that are trapped have come directly from your drain, making them easy to identify. Once you know what you're dealing with, you can easily get rid of drain flies by thoroughly cleaning the drain that they came from so there's no food source to attract them.

Fortunately, creating a trap for drain flies is easy. Find a clear container, such as a plastic cup or food container, and coat its inside with a light layer of petroleum jelly or vegetable oil. Alternatively, line the inside of the container with one or two glue boards for pests. The key is to ensure the inside of the trap has a sticky surface for the flies to get caught in. Set the container over the drain where you suspect the flies are coming from, and leave it in place for a day or so. If you find flies inside the trap when you check it, you can be sure they came from your sink drain. 

The good news is that eliminating a drain fly problem isn't that difficult. Once you remove their food source, they won't want to hang out in your sink. Drain flies also lay their eggs in the sludge in your drains, so thoroughly cleaning them removes the flies' food and eradicates them in their earliest life stages. You can use a commercially sold drain or toilet cleaner to dissolve the gunk that attracts flies. These cleaners are often available in biodegradable enzymatic formulas that pose less environmental risk as they work. These are ideal if you prefer to get rid of drain flies with natural products, but you can also skip the drain cleaner. Instead, use a long, stiff brush, such as a pipe-cleaning brush. For clogged drains, consider using a flexible drain brush, such as the Bozenu Flexible Drain Brush, to ensure you remove all of the build-up.

If you opt to clean your drain with a brush, it's also a good idea to use boiling water to flush the system completely. Pour boiling water down the drain to wash away loosened debris and melt any grease or other organic residue that might attract flies. Be cautious with PVC pipes, though, as frequent contact with boiling water can degrade them. Once you're certain that you've gotten rid of the drain flies, place a drain cover or screen over the drain to keep them from returning.